Longitudinal assessment of T-lymphocyte subpopulations during generalized demodicosis in dogs and their relationship with remission

Background The pathogenesis of canine generalized demodicosis is poorly understood but is thought to involve dysfunction of the immune system. Previous studies showed diminished CD4+ T lymphocyte counts in affected dogs, but none has evaluated this subpopulation through resolution of the disease. Hypothesis/Objectives In this longitudinal study, we tested whether quantification of CD4+ cells, CD8+ cells and the ratio of CD4+ to CD8+ cells are good indicators of immunological status and could be used as biomarkers of treatment efficacy and prognosis. Animals Sixteen dogs of several breeds with diagnoses of generalized demodicosis, plus 30 age/breedmatched healthy dogs. Methods Total lymphocytes, CD4+, CD8+ and CD4+:CD8+ ratio were quantified at four time points: at diagnosis, 30 days after diagnosis (during treatment), at first negative parasitological examination and at clinical cure. Results Absolute numbers of CD4+ cells were significantly lower in affected dogs at the time of diagnosis. Absolute numbers of CD4+ and CD8+ cells were significantly augmented in affected animals compared with control dogs after treatment was established, and this persisted until the first negative parasitological examination, at which time the CD4+ counts equalled those of the control group. Conclusions and clinical importance Our findings suggest that longitudinal quantification of CD4+ and CD8+ T lymphocytes is a useful indicator of the efficacy of demodicosis treatment. Résumé Contexte La pathogénie de la démodécie généralisée canine est mal comprise. On pense qu'elle implique un dysfonctionnement du système immunitaire. Les études précédentes montrent une baisse de lymphocytes T CD4+ chez les chiens atteints mais la sous‐population n'a jamais été étudiée au cours de la rémission clinique. Hypothèses/Objectifs Dans cette étude longitudinale, nous évaluons si la quantification des cellules CD4+, CD8+ et le ratio CD4+ à CD8+ sont de bons indicateurs du statut immunologique et pourraient être utilisés comme biomarqueurs d'efficacité et de pronostic de traitement. Sujets Seize chiens de différentes races avec un diagnostic de démodécie généralisée ainsi que 30 chiens sains d'âge et de races variés. Méthodes Les lymphocytes totaux, les CD4+, CD8+ et le ratio CD4+:CD8+ ont été quantifiés à quatre reprises: au moment du diagnostic, 30 jours après le diagnostic (au cours du traitement), au premier examen parasitaire négatif et à la fin du traitement. Résultats Les nombres absolus